As a fuel cell system comprising a fuel cell and a load connected to the fuel cell, a system described in Patent Document 1 is known. In the system, the output voltage of the fuel cell is raised by a first DC/DC converter and output to the load. Moreover, when the only output of the fuel cell is supplied, a power necessary for the load runs short. In this case, a power to compensate for the shortage is output from an accumulator to the load via a second DC/DC converter. When the output power of the fuel cell exceeds the power of the load, the power is supplied from the fuel cell to the accumulator through the first and second DC/DC converters to charge the accumulator.
In a control device of the fuel cell system described Patent Document 1, the target power of a motor as the load is calculated. The control device calculates the target voltage of the motor in accordance with the target power thereof, to calculate the target output current of the fuel cell. The control device feedback-controls the target output current as the target current of the first DC/DC converter, and feedback-controls the target voltage of the motor as the target voltage of the second DC/DC converter. Moreover, the fuel cell system has an inverter. The inverter converts a direct-current electric power output from the second DC/DC converter into an alternating-current power to output the power to a motor.